Background Foot problems developing during the disease course of rheumatoid arthritis (RA) patients can cause decreased mobility and quality of life. Orthopedic shoes may help to reduce pain and increase activity participation in RA patients.
Objectives To investigate if foot damage due to RA can predict if patients will wear orthopedic shoes within 10 years after treatment start.
Methods In the four treatment arms of the BeSt study, 508 patients with recent onset RA were treated to target (disease activity score (DAS) ≤2.4). After 10 years, patients were asked if they used orthopedic shoes.
Univariable binary logistic regression was performed with orthopedic shoe use as outcome variable and baseline total Sharp/van der Heijde score (SHS), foot erosions and foot joint space narrowing (JSN) as continuous and binary variables (score >0.5 yes/no) as potential predictors. Next, rheumatoid factor (RF), smoking (yes/no), anti-citrullinated protein antibodies (ACPA), DAS and age were simultaneously added as predictors in a multivariable model, in combination with the statistically significant predictors (p<0.1) from the univariable regression. Only predictors with statistically significant contribution were kept in the final model. Interaction of each predictor with treatment arm was tested.
Results Of 285/508 patients (56.1%) information was available regarding orthopedic shoe use. Responders were younger than non-responders [age mean (SD) 51.3 (12.0) vs 58.4 (14.8) years, p<0.001], but did not differ statistically significant in gender, smoking status, DAS, SHS, JSN or erosions (all at baseline). Twenty percent (57/273) of the patients reported orthopedic shoes use after 10 years [68.4% female, mean (SD) age 50.3 (11.0) years, DAS 4.6 (0.9), SHS 4.7 (5.3), erosions 1.0 (2.3), JSN 1.0 (1.9), ACPA+ 83.3%, RF+ 77.2%, all at baseline]. Orthopedic shoe users were more often ACPA+ (77.2% vs. 65.8%) and had more erosions [mean (SD) 1.25 (2.43) vs. 0.48 (2.48), all p<0.05]. No predictor had a significant interaction with allocated treatment group. Univariable logistic regression showed that only foot erosions had a significant contribution to the model as binary variable (OR 1.95), but not as continuous variable (OR 1.06). Neither total SHS nor foot-JSN (binary or continuous) contributed significantly to the model (OR 1.61 and 1.03 for SHS; 1.59 and 1.08 for foot-JSN, respectively). Multivariable logistic regression showed that baseline presence of foot erosions (binary; OR 1.85), ACPA+ (OR 4.88) and DAS (OR 1.72) were independent predictors of orthopedic shoe use after 10 years. Combining foot erosions (binary; OR 1.87), ACPA (OR 4.46) and DAS (OR 1.73) resulted in the best model (see table 1).
Conclusions Despite 10 years of DAS ≤2.4 targeted treatment, 20% of recent onset RA patients with available data after 10 year used orthopedic shoes. Presence of foot erosions at treatment start predicts the use of orthopedic shoes after 10 years. The risk of orthopedic shoe use increases for ACPA+ patients and to a lesser extent for patients with higher baseline DAS.
Disclosure of Interest S. Bergstra: None declared, R. van den Berg: None declared, C. Bijkerk: None declared, A. Gerards: None declared, R. Goekoop: None declared, P. Kerstens: None declared, W. Lems: None declared, T. Huizinga: None declared, R. Landewé: None declared, C. Allaart Grant/research support from: The study was designed by the investigators and supported by a government grant from the Dutch Insurance Companies, with additional funding from Schering-Plough B.V. and Janssen B.V. Data collection, trial management, data analysis and preparation of the manuscript were performed by the authors.